Freeway median widths, as a general rule...

[Tom958]

A big topic that's probably been broached before...

In my own state of Georgia, the first rural Interstates were built with 40-foot medians. In the early '60's, the standard changed to 64 feet, where it's essentially remained ever since. The only exceptions were on the last rural sections of I-20 (Alabama to GA 5) and I-85 (I-185 to  Grantville) where they went to 88 feet to provide for eventual widening, and the rural parts of I-185, for which I have no explanation. Non-Interstate rural freeways are scarce in Georgia, but they were generally a scootch inferior to Interstates: 40-foot medians for various bypasses and a lack of bifurcations on GA 400- - or I-575, which I suspect was designed as a state project. More recently, the few non-Interstate freeway segments use the same 44-foot medians as divided at-grade highways.

Why am I telling you this? Because I believe, perhaps erroneously, that this is the pattern that most states follow.

Then there's North Carolina. It, too, started out with 40-foot medians for rural Interstates, then went to 68 feet in the early to mid '60's. However, in the late '80's they used 46-foot medians for the remaining sections of I-40: the Winston Salem bypass, the Durham-Chapel Hill-RTP section, and the entire stretch from Raleigh to Wilmington! My first thought, nearly thirty years ago when I first noticed the narrow median on new 40 near W-S, was that it had been designed as a state project and FHWA didn't make them redesign it to provide a sixtyish-foot median. However, after broaching the topic in a North Carolina-centric Facebook group, it seems that that wasn't the case. It could be that 46 feet was intended to provide for an eventual two more lanes, ten foot left shoulders, and a Jersey barrier. That seems unlikely for the entire Raleigh-Wilmington route.

Meanwhile, while some of NC's numerous non-Interstate freeways were built with 46-foot medians, many others weren't. US 311 tying into new 40 and built at the same time, had 68 feet, as did many others. I found 86 feet on US 220 around Emery and Candor, 96 feet on US 70 between Kinston and New Bern, and possibly 100 feet on 421 between Greensboro and Siler City (OK, this was built as an at-grade highway, which may have something to do with it). Found a couple of narrower widths, too, like 56-60 feet, including the '80's section of I-95 from Kenly to Rocky Mount: 60 feet, not the standard 68. Wassup with that? 95 at Fayetteville is 92 feet, though.

OK, I know that policies are guidelines, not hard-and-fast rules (and let's set aside complicating factors such as urban obstacles or mountainous terrain!). Still, what North Carolina has done, whatever its merits, looks more like Calvinball than policy.

So...

Anyone know anything about why things in North Carolina are the way they are?

Are there other states that where policy is as malleable as it appears to be in North Carolina?

Is the situation I described in Georgia really the norm, or is the real world quite a bit more nuanced?

[Beltway]

Are there other states that where policy is as malleable as it appears to be in North Carolina?

Virginia has never had a standard width for rural Interstate highways, that I know of.  Some miles are narrow as in about 40 feet, a few are less, many miles of highway have independently graded roadways with variable width medians ranging from about 80 feet to about 200 feet and sometimes wider.

[kphoger]

A big topic that's probably been broached before...

If it's been discussed before, I certainly don't remember it.  The closest thread I can recall was one about the widest median–not about typical median widths.

[webny99]

Imagine the width of a narrow median. Divide by 4. You now have the average median width for freeways in Pennsylvania.

[jeffandnicole]

A big topic that's probably been broached before...

In my own state of Georgia, the first rural Interstates were built with 40-foot medians. In the early '60's, the standard changed to 64 feet, where it's essentially remained ever since. The only exceptions were on the last rural sections of I-20 (Alabama to GA 5) and I-85 (I-185 to  Grantville) where they went to 88 feet to provide for eventual widening, and the rural parts of I-185, for which I have no explanation. Non-Interstate rural freeways are scarce in Georgia, but they were generally a scootch inferior to Interstates: 40-foot medians for various bypasses and a lack of bifurcations on GA 400- - or I-575, which I suspect was designed as a state project. More recently, the few non-Interstate freeway segments use the same 44-foot medians as divided at-grade highways.

Why am I telling you this? Because I believe, perhaps erroneously, that this is the pattern that most states follow.

Then there's North Carolina. It, too, started out with 40-foot medians for rural Interstates, then went to 68 feet in the early to mid '60's. However, in the late '80's they used 46-foot medians for the remaining sections of I-40: the Winston Salem bypass, the Durham-Chapel Hill-RTP section, and the entire stretch from Raleigh to Wilmington! My first thought, nearly thirty years ago when I first noticed the narrow median on new 40 near W-S, was that it had been designed as a state project and FHWA didn't make them redesign it to provide a sixtyish-foot median. However, after broaching the topic in a North Carolina-centric Facebook group, it seems that that wasn't the case. It could be that 46 feet was intended to provide for an eventual two more lanes, ten foot left shoulders, and a Jersey barrier. That seems unlikely for the entire Raleigh-Wilmington route.

Meanwhile, while some of NC's numerous non-Interstate freeways were built with 46-foot medians, many others weren't. US 311 tying into new 40 and built at the same time, had 68 feet, as did many others. I found 86 feet on US 220 around Emery and Candor, 96 feet on US 70 between Kinston and New Bern, and possibly 100 feet on 421 between Greensboro and Siler City (OK, this was built as an at-grade highway, which may have something to do with it). Found a couple of narrower widths, too, like 56-60 feet, including the '80's section of I-95 from Kenly to Rocky Mount: 60 feet, not the standard 68. Wassup with that? 95 at Fayetteville is 92 feet, though.

OK, I know that policies are guidelines, not hard-and-fast rules (and let's set aside complicating factors such as urban obstacles or mountainous terrain!). Still, what North Carolina has done, whatever its merits, looks more like Calvinball than policy.

So...

Anyone know anything about why things in North Carolina are the way they are?

Are there other states that where policy is as malleable as it appears to be in North Carolina?

Is the situation I described in Georgia really the norm, or is the real world quite a bit more nuanced?

Other than I believe 60 feet is the minimum width of a median without barrier protection, median width is probably up to right-of-way, potential future uses, etc. 

I think looking at every single interstate's median width is probably reading a bit too much into it.  If you look at the entire written history of each highway's planning, maybe they have their reasoning in there. 

[AsphaltPlanet]

Median width may have had something to do with available property.

Or it's not impossible that property was set aside for an interstate years before shovels actually hit the ground and a narrow median is built on newer construction for that reason.

In Ontario, the 407 was built in the 1990s.  On land that the province started setting aside in the 1950s.  So some design elements of the 407 were probably limited because of decisions that were made 40 years ago.  It wouldn't shock me if there was a similar case in North Carolina.

[Tom958]

My internet's down, so I'm doing this on my phone:

@kphoger: Thanks!

@jeffandnicole: 60 feet may be a break point for whether or not a barrier is required now, but it wasn't in the late '80's when NC started building rural Interstates with 46 foot medians instead of 68. Continuous barriers weren't installed on those highways until the cable barrier era, at which point they appeared in some 68 foot medians as well.

Also, Alabama's standard median width was 55+/- when other states generally went to 60 or more, and they didn't install continuous barriers.

As for checking so many median widths, well... it was a matter of one thing leading to another. It didn't occur to me that I-40 might have a narrow median all the way to Wilmington until a discussion convinced me that the other  '80's, narrow median Interstates I knew about, all of which were near cities, had been scoped as Interstates from their inception. Also, one fellow provided a list of medians that he thought were especially wide, and I checked every one out of both genuine interest and courtesy. Most were actually 68 feet, btw. I guess that the presence of numerous stretches of legacy narrow medians in NC makes 68 foot medians seem wider than they really are. 

[Flint1979]

I'm not totally sure on the widths but there are some really wide medians out there. I know on I-24 in Tennessee there's one that's pretty wide and just north of Cincinnati you have the village of Arlington Heights which sits in the median of I-75.

[billpa]

Imagine the width of a narrow median. Divide by 4. You now have the average median width for freeways in Pennsylvania.

Perhaps another thread should be started about the amount of space between the outer edges of interstates and where private properties begin. In Pennsylvania I always feel that buildings along interstate highways are closer to the roadway than almost anywhere else.

Pixel 2

[mrsman]

Imagine the width of a narrow median. Divide by 4. You now have the average median width for freeways in Pennsylvania.

Perhaps another thread should be started about the amount of space between the outer edges of interstates and where private properties begin. In Pennsylvania I always feel that buildings along interstate highways are closer to the roadway than almost anywhere else.

Pixel 2

This seems especially true along I-95 in Chester, PA.  My wife always jokes that if traffic were bad, you could just reach out and say hello to the people who live right along there.

[Flint1979]

Imagine the width of a narrow median. Divide by 4. You now have the average median width for freeways in Pennsylvania.

Perhaps another thread should be started about the amount of space between the outer edges of interstates and where private properties begin. In Pennsylvania I always feel that buildings along interstate highways are closer to the roadway than almost anywhere else.

Pixel 2

This seems especially true along I-95 in Chester, PA.  My wife always jokes that if traffic were bad, you could just reach out and say hello to the people who live right along there.

I never understood why anyone would want to live in any of those houses. You look out your window and there's I-95 right in front of you.

[DJStephens]

They probably inherited them from their parents.  No mortgage is certainly a good thing.  But seriously with the expense of housing in the NE, sometimes sacrifices have to be made.   

[jeffandnicole]

Imagine the width of a narrow median. Divide by 4. You now have the average median width for freeways in Pennsylvania.

Perhaps another thread should be started about the amount of space between the outer edges of interstates and where private properties begin. In Pennsylvania I always feel that buildings along interstate highways are closer to the roadway than almost anywhere else.

Pixel 2

This seems especially true along I-95 in Chester, PA.  My wife always jokes that if traffic were bad, you could just reach out and say hello to the people who live right along there.

I never understood why anyone would want to live in any of those houses. You look out your window and there's I-95 right in front of you.

If you're living in Chester, you probably don't have much money to begin with to be too picky about location.

[jeffandnicole]

@jeffandnicole: 60 feet may be a break point for whether or not a barrier is required now, but it wasn't in the late '80's when NC started building rural Interstates with 46 foot medians instead of 68. Continuous barriers weren't installed on those highways until the cable barrier era, at which point they appeared in some 68 foot medians as well.

Also, Alabama's standard median width was 55+/- when other states generally went to 60 or more, and they didn't install continuous barriers.

Definitely not a "now" rule. And it's something that could vary between states, or based on the design of the median which is intended not only for drainage, but to capture cars that veer into the median. As you noted, many highways are now getting barriers regardless of their width.

[Flint1979]

Imagine the width of a narrow median. Divide by 4. You now have the average median width for freeways in Pennsylvania.

Perhaps another thread should be started about the amount of space between the outer edges of interstates and where private properties begin. In Pennsylvania I always feel that buildings along interstate highways are closer to the roadway than almost anywhere else.

Pixel 2

This seems especially true along I-95 in Chester, PA.  My wife always jokes that if traffic were bad, you could just reach out and say hello to the people who live right along there.

I never understood why anyone would want to live in any of those houses. You look out your window and there's I-95 right in front of you.

If you're living in Chester, you probably don't have much money to begin with to be too picky about location.

No way could I disagree with that.

[Rick Powell]

Around my area of IL, there is the fairly narrow median of 40 feet on I-80 west of Morris, the very wide median of 88 feet on I-55 south of Dwight, and the in between median of 54 feet on I-39 south of Oglesby. The only one of the three IDOT has installed cable guard is I-80. When I-80 was reconstructed between Brisbin Road and Minooka, they widened everything to the inside and put a Jersey barrier down the middle.

The I-80 section dates to 1960, the I-55 section around 1977, and I-39 in the early 90's. I know that I-39 had a wider median designed, but farmland preservation was becoming an issue and the width was negotiated downward.

[Roadsguy]

Imagine the width of a narrow median. Divide by 4. You now have the average median width for freeways in Pennsylvania.

Perhaps another thread should be started about the amount of space between the outer edges of interstates and where private properties begin. In Pennsylvania I always feel that buildings along interstate highways are closer to the roadway than almost anywhere else.

Pixel 2

This seems especially true along I-95 in Chester, PA.  My wife always jokes that if traffic were bad, you could just reach out and say hello to the people who live right along there.

I never understood why anyone would want to live in any of those houses. You look out your window and there's I-95 right in front of you.

I've heard that when PennDOT was planning the widening they want to do through there (an auxiliary lane for the section with 322), the people on each side were fighting not to keep their homes, but for the road to be widened onto their side because living next to I-95 is so bad.

[Flint1979]

Imagine the width of a narrow median. Divide by 4. You now have the average median width for freeways in Pennsylvania.

Perhaps another thread should be started about the amount of space between the outer edges of interstates and where private properties begin. In Pennsylvania I always feel that buildings along interstate highways are closer to the roadway than almost anywhere else.

Pixel 2

This seems especially true along I-95 in Chester, PA.  My wife always jokes that if traffic were bad, you could just reach out and say hello to the people who live right along there.

I never understood why anyone would want to live in any of those houses. You look out your window and there's I-95 right in front of you.

I've heard that when PennDOT was planning the widening they want to do through there (an auxiliary lane for the section with 322), the people on each side were fighting not to keep their homes, but for the road to be widened onto their side because living next to I-95 is so bad.

Some of that is just ridiculous. I don't understand why there isn't a noise barrier in that area. The worst of it in Chester looks like it's along Forwood Street on both sides of I-95.

[intelati49]

... Anyways, back on topic

In Missouri

On I-44 the median width is seemingly 20ft (Probably 30ft) on the oldest stretches between Rolla and Springfield. Once you get past the old Route 66 exit west of there, the median width increases to something between 40-50ft (1980s).

I-49 south of I-44 meets the current standard of 60ft. It really is amazing the different feel between those three sections of road.

[J N Winkler]

A big topic that's probably been broached before...

There has been (IIRC) some discussion of median widths in terms of requirements for cable barrier.  I know I have shoveled contumely on top of MoDOT (or, to be precise, its predecessor agencies) for building I-70 across Missouri with a 40 ft median.

In my own state of Georgia, the first rural Interstates were built with 40-foot medians. In the early '60's, the standard changed to 64 feet, where it's essentially remained ever since. The only exceptions were on the last rural sections of I-20 (Alabama to GA 5) and I-85 (I-185 to  Grantville) where they went to 88 feet to provide for eventual widening, and the rural parts of I-185, for which I have no explanation. Non-Interstate rural freeways are scarce in Georgia, but they were generally a scootch inferior to Interstates: 40-foot medians for various bypasses and a lack of bifurcations on GA 400- - or I-575, which I suspect was designed as a state project. More recently, the few non-Interstate freeway segments use the same 44-foot medians as divided at-grade highways.

Why am I telling you this? Because I believe, perhaps erroneously, that this is the pattern that most states follow.

It is certainly generally true, in most states, that design parameters such as median width and overall right-of-way width became more generous as freeway construction progressed.  Probably the greatest variation among states relates to non-Interstate freeways.  Many states chose to apply Interstate standards, while others did not.

Anyone know anything about why things in North Carolina are the way they are?

I know just enough to make educated guesses.  The 1980's were a time of fiscal constraint in NC and resulted in major corridors that really should have been built as freeway from the start, and are currently being slowly upgraded to that standard, being expanded instead to divided highways with little control of access.  US 70 is the classic example.  I suspect that I-40 was built with a narrow median to save money, though the savings would have been modest compared to the overall construction cost given that the terrain it passes through east of Raleigh is swamp or low-value agricultural land.  I-40 east of Greensboro is not part of the original Interstate system (extension to I-95 approved in 1969, further extension to Wilmington approved in 1984), so ten-cent dollars were not available to build it.

Is the situation I described in Georgia really the norm, or is the real world quite a bit more nuanced?

Choice of standard median width is an engineering policy decision that is often driven by economic and fiscal considerations specific to each state.  Some states, like Georgia, have chosen to build non-Interstate freeways to standards noticeably inferior to Interstates, while in others like Kansas, non-Interstate freeways have been built more or less to Interstate standards since the 1970's.

Similar observations apply to overall right-of-way width and to other cross-sectional elements such as shoulders, side slope treatments, etc.

@jeffandnicole: 60 feet may be a break point for whether or not a barrier is required now, but it wasn't in the late '80's when NC started building rural Interstates with 46 foot medians instead of 68. Continuous barriers weren't installed on those highways until the cable barrier era, at which point they appeared in some 68 foot medians as well.

If we have national standards governing the use of cable barrier in vegetated medians, I am not aware of them.  (I suspect they are coming.)  The only standards I know of deal with concrete Jersey barrier in paved medians.  Cable barrier in medians ranging in width from 40 ft to about 60 ft are pretty common now.  Oklahoma uses cable barrier at 80 ft.

[Tom958]

It is certainly generally true, in most states, that design parameters such as median width and overall right-of-way width became more generous as freeway construction progressed.  Probably the greatest variation among states relates to non-Interstate freeways.  Many states chose to apply Interstate standards, while others did not.

One Georgia item I omitted in the interest of brevity was that, as of the date of the public meetings I attended in the late '80's-early '90's, the median width for the Outer Perimeter was to be 92 feet, which was upped to 102 feet for the Northern Arc. Nothing like that was ever built, though.

Anyone know anything about why things in North Carolina are the way they are?

I know just enough to make educated guesses.  The 1980's were a time of fiscal constraint in NC and resulted in major corridors that really should have been built as freeway from the start, and are currently being slowly upgraded to that standard, being expanded instead to divided highways with little control of access.  US 70 is the classic example.  I suspect that I-40 was built with a narrow median to save money, though the savings would have been modest compared to the overall construction cost given that the terrain it passes through east of Raleigh is swamp or low-value agricultural land.  I-40 east of Greensboro is not part of the original Interstate system (extension to I-95 approved in 1969, further extension to Wilmington approved in 1984), so ten-cent dollars were not available to build it.

Another aspect of this is that I-40 from Raleigh to Wilmington was built essentially in one piece, with the bridge dates on Bridgereports.com ranging from 1986 to 1988. The part between I-85 and the RTP was 1986-87, as was US 321 north of Gastonia, and the Winston Salem bypass followed in 1989-1991. That would've been a heavy lift under any circumstances.

The big question to me, though, is why the Feds went for it. For the sections west of Raleigh (or, for that matter, west of I-95), 46 feet could've been spun as provision for an eventual two more lanes, ten foot left shoulders and a Jersey barrier. To the east, though, any cost savings must've been trivial due to the low value and benign nature of the terrain, as you pointed out.

I could imagine a logical argument being made that of 46 feet was adequate for the more heavily traveled sections near W-S and Chapel Hill, then it should be more than adequate for the lightly used sections east of 95. So, why ever go back to 68 feet? 

[DJStephens]

[If we have national standards governing the use of cable barrier in vegetated medians, I am not aware of them.  (I suspect they are coming.)  The only standards I know of deal with concrete Jersey barrier in paved medians.  Cable barrier in medians ranging in width from 40 ft to about 60 ft are pretty common now.  Oklahoma uses cable barrier at 80 ft.
[/quote]

New Mexico has quite a bit of older Interstate (early sixties) that should have cable barriers.  I-10 west of las Cruces.  Sections of I-25 south of Hot Springs (truth or consequences), and I-40, both east and west of Albuquerque.   Some of these older sections, could have been reconstructed by now, with wider medians, better sight lines, and new interchanges replacing the originals.  The recent bus crossover / crash on I-40 near Thoreau illustrated this quite well.   And the more recent four lane jobs - with only a painted stripe median?  Not even going to go into detail on how bad those are.   

[Tom958]

Around my area of IL, there is the fairly narrow median of 40 feet on I-80 west of Morris, the very wide median of 88 feet on I-55 south of Dwight, and the in between median of 54 feet on I-39 south of Oglesby. The only one of the three IDOT has installed cable guard is I-80. When I-80 was reconstructed between Brisbin Road and Minooka, they widened everything to the inside and put a Jersey barrier down the middle.

The I-80 section dates to 1960, the I-55 section around 1977, and I-39 in the early 90's. I know that I-39 had a wider median designed, but farmland preservation was becoming an issue and the width was negotiated downward.

Interesting. Sounds similar to North Carolina, except for the known rationale for the narrower median on I-39. That said, just randomly clicking around Illinois, I find a good bit of variation in the 60-70 foot range. Despite the variations, I think it's fair to say that 68 feet is NC's standard median width. I'm not sure it's possible to make a similar statement about Illinois.

... Anyways, back on topic

Thanks!

In Missouri

On I-44 the median width is seemingly 20ft (Probably 30ft) on the oldest stretches between Rolla and Springfield. Once you get past the old Route 66 exit west of there, the median width increases to something between 40-50ft (1980s).

I-49 south of I-44 meets the current standard of 60ft. It really is amazing the different feel between those three sections of road.

Indeed. I mentioned earlier how badly my NC friends did at gauging median widths by eye when narrow and wider ones are both common.

I'm not totally sure on the widths but there are some really wide medians out there. I know on I-24 in Tennessee there's one that's pretty wide...

The first time I did anything like this was for a series of posts about I-24 from Chattanooga to Nashville. Construction proceeded more or less westward from Chattanooga, and it was easy to see how TDOT's philosophy evolved during the '60's peak of Interstate construction.  Regarding median width, it went from 60 feet coming off of Monteagle to 100 feet, then eventually to 120 feet between McMinnville and the edge of Nashville, though it went back to 60 near towns and across one pass.

[Flint1979]

Around my area of IL, there is the fairly narrow median of 40 feet on I-80 west of Morris, the very wide median of 88 feet on I-55 south of Dwight, and the in between median of 54 feet on I-39 south of Oglesby. The only one of the three IDOT has installed cable guard is I-80. When I-80 was reconstructed between Brisbin Road and Minooka, they widened everything to the inside and put a Jersey barrier down the middle.

The I-80 section dates to 1960, the I-55 section around 1977, and I-39 in the early 90's. I know that I-39 had a wider median designed, but farmland preservation was becoming an issue and the width was negotiated downward.

Interesting. Sounds similar to North Carolina, except for the known rationale for the narrower median on I-39. That said, just randomly clicking around Illinois, I find a good bit of variation in the 60-70 foot range. Despite the variations, I think it's fair to say that 68 feet is NC's standard median width. I'm not sure it's possible to make a similar statement about Illinois.

... Anyways, back on topic

Thanks!

In Missouri

On I-44 the median width is seemingly 20ft (Probably 30ft) on the oldest stretches between Rolla and Springfield. Once you get past the old Route 66 exit west of there, the median width increases to something between 40-50ft (1980s).

I-49 south of I-44 meets the current standard of 60ft. It really is amazing the different feel between those three sections of road.

Indeed. I mentioned earlier how badly my NC friends did at gauging median widths by eye when narrow and wider ones are both common.

I'm not totally sure on the widths but there are some really wide medians out there. I know on I-24 in Tennessee there's one that's pretty wide...

The first time I did anything like this was for a series of posts about I-24 from Chattanooga to Nashville. Construction proceeded more or less westward from Chattanooga, and it was easy to see how TDOT's philosophy evolved during the '60's peak of Interstate construction.  Regarding median width, it went from 60 feet coming off of Monteagle to 100 feet, then eventually to 120 feet between McMinnville and the edge of Nashville, though it went back to 60 near towns and across one pass.

Without putting much into it doesn't it get to be about a mile in that median where it's extremely wide? I know of a few others but can't think of them right now. The I-75 median in Arlington Heights, Ohio has always caught my eye every time I've traveled through Cincinnati. I thought wow this looks pretty cool there's a city in the middle of I-75 and that's always my tell all sign that I'm almost to Cincinnati.

[kphoger]

Oklahoma uses cable barrier at 80 ft.

And Oklahoma also uses cable barriers with basically no median at all.  On an Interstate.